The present invention relates to the field of rocketry and, more specifically, to power units with liquid-propellant rocket engines.
Known in the art and widely used in launch vehicles for various applications are liquid-propellant rocket engines operating on liquid oxygen and such hydrocarbon fuel, as kerosene. These fuel components are used, for instance, by US liquid-propellant rocket engine LR-105-NA (see the xe2x80x9cKosmonavtikaxe2x80x9d encyclopedia, Moscow, 1985, page 218, article LR-105-NA). This engine has a specific impulse of 2153 m/s on the ground, and 3025 m/s in vacuum. Let us assume that the method of getting the specific impulse from interaction of the aforesaid fuel components in the LR-105-NA liquid-propellant rocket engine is analogous to the method disclosed in the present invention. The disadvantage of the known method consists in that it fails to use a considerable reserve for increasing the specific impulse of the liquid-propellant rocket engine which could be exploited by finding a more effective hydrocarbon fuel than kerosene.
Known in the art is liquid-propellant rocket engine RD-301 of the GDL-OKB design (see the xe2x80x9cKosmonavtikaxe2x80x9d encyclopedia, Moscow, 1985, page 331, article RD-301). This engine uses liquid fluorine as oxidant and liquid ammonia as fuel. The engine specific impulse in vacuum is equal to 3928 m/s.
Let us assume that the method of getting the specific impulse from interaction of the aforesaid fuel components in the RD-301 liquid-propellant rocket engine is analogous to the method disclosed in the present invention. The known method is deficient in that the use of such effective fuel components as ammonia and fluorine in the aforesaid engine calls for a considerable sophistication of the design of many of its accessories, units and components as compared with a similar engine operating on a combination of liquid oxygen and such hydrocarbon fuel as kerosene. Besides, what with today""s technological level in rocketry, the use of the known method for increasing the engine specific impulse would tend to raise the cost of research and development work and, in the final count, would make the accomplishment of concrete projects too expensive.
US patents also disclose a number of technical solutions pertaining to the improvement of fuel components for liquid-propellant rocket engines. Specifically, this problem is dealt with in the inventions disclosed in U.S. Pat. Nos. 3,097,479, 3,127,735, 3,230,700, which are also assumed here as analogous to the method disclosed in the present invention. The aforesaid analogous art gives no indication of the use of fuel in liquid oxygen rocket engines that would be similar to kerosene, but provide a higher specific impulse.
Liquid oxygen and kerosene are used as fuel components by known liquid-propellant rocket engine RD-107 of the GDL-OKB design (see the xe2x80x9cKosmonavtikaxe2x80x9d encyclopedia, Moscow, 1985, pages 327-329, article RD-107). This engine has a specific impulse of 2520 m/s on the ground, and 3080 m/s in vacuum. We shall assume the method of getting the aforesaid specific impulse from the interaction of the aforementioned fuel components used in the RD-107 liquid-propellant rocket engine as the prototype of the proposed method in the present invention. The shortcoming of this prior art method consists in that it fails to exploit the available reserve for improving the specific impulse of the liquid-propellant rocket engine by using a hydrocarbon fuel that would be more effective than kerosene and would not call for any essential and radical changes in the engine design.
Recent years have been marked by the increasing popularity of rocket power units with liquid-propellant rocket engines. A power unit of this kind was described, for instance, in the monograph xe2x80x9cLaunch vehiclesxe2x80x9d (ed. Prof. S. O. Osipov), Moscow, 1981, Voenizdat, Chapter 6, pages 202-203. FIG. 6.1 of this monograph illustrates diagrammatically a power unit with a turbo-pump system for supply of fuel components. This power unit includes a liquid-propellant rocket engine comprising a turbo-pump system for supply of oxidant and fuel, an oxidant tank and a fuel tank, as well as automatic control system components. The fuel tank is filled with the required quantity of fuel, whereas the oxidant tank carries the required quantity of oxidant.
Let us assume that this power unit is analogous to the proposed rocket power unit. The analogous art is deficient in that it fails to indicate definite fuel components for which the power unit in question was designed, wherefore the efficiency of said power unit cannot be evaluated.
Known in the art is a 1st stage power unit of the American Saturn-I launch vehicle (see the xe2x80x9cKosmonavtikaxe2x80x9d encyclopedia, chief editor V. P. Glushko, Moscow, 1985, page 322, article xe2x80x9cRocket power unitxe2x80x9d; page 346, article xe2x80x9cSaturnxe2x80x9d; and page 444, article xe2x80x9cN-1xe2x80x9d).
This 1st stage power unit consists of 8 liquid-propellant rocket engines N-1 and runs on two-component fuel (the oxidant being liquid oxygen). The engine is provided with a turbo-pump fuel supply system. The rocket engine power unit in question also comprises oxidant and fuel tanks and automatic control equipment. The oxidant tank is filled with the required amount of liquid oxygen, whereas the fuel tank carries the corresponding amount of hydrocarbon fuel (kerosene).
We shall assume this technical solution to be analogous to the proposed rocket power unit. The prior art is deficient in that the fuel tank in the known power unit is filled with kerosene which is not the best fuel for this unit.
Known in the art is a 1st rocket power unit of the R-9 intercontinental ballistic missile which uses fuel consisting of two main components, oxygen and kerosene (see the book entitled xe2x80x9cRocket-space corporation Energy named after S. P. Korolevxe2x80x9d, ed. Semionov Yu. P., 1996, pages 121 and 122).
The oxidant tank of the R-9 missile is filled with the required amount of liquid oxygen, whereas the fuel tank carries the corresponding amount of hydrocarbon fuel (kerosene).
We shall assume this technical solution to be the prototype of the proposed rocket power unit. The prototype is deficient in that its fuel tank is filled with kerosene which is not the best fuel for this unit, as the specific impulse in its liquid-propellant rocket engine can be higher.
It is an object of the present invention to identify a hydrocarbon fuel which would have physical, chemical and service properties approximating to those of kerosene and make it possible to increase the specific impulse in the liquid-propellant rocket engine using liquid oxygen and kerosene as fuel components without appreciable changes in its design.
This task was prompted by the feasibility of effective renovation of liquid-propellant rocket engines and rocket power units with such engines operating on oxygen-kerosene fuel components.
The results of theoretical and experimental studies have shown that a combination of hydrocarbon fuel having a polycyclic structure with oxygen may increase the heating capacity of fuel due to the optimization of the carbon-hydrogen ratio in fuel and the enthalpy of its formation from these elements.
The hydrocarbon fuel sought is dicyclobutyl (C8H14) which, when used with liquid oxygen, may increase the specific impulse in the RD-107 liquid-propellant rocket engine mentioned above by approximately 2%.
The essence of the disclosed method for increasing the specific impulse in a liquid-propellant rocket engine consists in that the liquid-propellant rocket engine designed for operation on oxygen and liquid hydrocarbon fuel is supplied with liquid oxygen as oxidizer and dicyclobutyl (C8H14) as hydrocarbon fuel. The physical, chemical and service properties of dicyclobutyl (high density, boiling and freezing points, thermal stability, cooling properties) come near to those of kerosene thereby making it a good substitute.
As regards liquid-propellant rocket engines, the proposed method has the advantage of increasing the engine specific impulse over the methods of operating engines on liquid oxygen and kerosene. It is worth noting that such a hydrocarbon fuel as methane with oxygen provides even a higher specific impulse than dicyclobutyl, but its use calls for essential changes in the design of oxygen-kerosene rocket engines.
The Table that follows presents estimated impulse values against mass relations of fuel components (oxidant to fuel) Km at a pressure of 260 kgf/cm2 in the combustion chamber with nozzle area geometric expansion being equal to 36.9. In this table the column xe2x80x9cDicyclobutylxe2x80x9d presents impulse values for fuel components liquid oxygenxe2x80x94dicyclobutyl, and the column xe2x80x9cKerosenexe2x80x9d, impulse values for fuel components liquid oxygenxe2x80x94kerosene. These values have been mainly defined for type RD-107 liquid-propellant rocket engines with generator gas afterburning in the chamber.
The table shows that the specific impulse in oxygen rocket engines of similar design increases by approximately 2% when they use dicyclobutyl instead of kerosene.
In some applications the best mass relations of fuel components (oxidant to fuel) for high and medium power liquid-propellant rocket engines fall within an interval of 2.4 to 3. These relations are advantageous, as they provide the highest values of the specific impulse in the corresponding rocket engines. However, the table also shows that other relationships of fuel components, e.g. 2 or 3.5, need not be disregarded either, though they may lead sometimes to a substantial decrease of the advantages of the proposed method.
In other particular applications of the disclosed method the pressure in the combustion chamber of liquid-propellant rocket engines must be maintained within a range of 50 to 300 kgf/cm2. At lower, though also possible, pressures in the combustion chamber it is difficult to attain desired high values of the specific impulse, whereas pressures exceeding the maximum limit of the indicated range may affect the performance of certain engine components for strength reasons.
The technical result of the disclosed method consists in the identification of hydrocarbon fuel dicyclobutyl (C8H14) which possesses physical, chemical and service properties approximating to those of kerosene and, when used jointly with liquid or gaseous oxygen as oxidizer, makes it possible to increase the specific impulse of the liquid-propellant rocket engine by approximately 2% as compared with the oxygen-kerosene rocket engine (see also the Table presented above).
Another technical result of the disclosed method consists in the identification of a fuel for hydrocarbon-oxygen rocket engines that does not call for any essential changes in engines operating on oxygen-kerosene fuel.
The object of the proposed rocket power unit was to supply the liquid-propellant rocket engine of a rocket power unit with a fuel that would enable the engine to develop a higher specific impulse in an oxygen liquid-propellant rocket engine than kerosene and yet come near to kerosene in its physical, chemical and technical properties.
The essence of the invention xe2x80x9cRocket power unit for realizing the methodxe2x80x9d consists in that the disclosed power unit comprises at least one liquid-propellant rocket engine, oxidant and fuel tanks, a system (systems) for supply of oxidant and fuel, as well as automatic equipment accessories, said oxidant tank being filled with the required quantity of oxygen, preferably liquid, and said fuel tank being filled with the required quantity of dicyclobutyl (C8H14). In principle, the aforesaid tanks may be filled with fuel components to capacity.
In one of the embodiments of the invention the temperature of dicyclobutyl in the tank varies from xe2x88x9250xc2x0 C. to +50xc2x0 C.
The technical result of the implementation of the disclosed invention consists in a possibility of increasing the liquid-propellant rocket engine specific impulse, thrust and in-flight operating time, or reducing the weight of the tanks (both empty and full) without essential changes in the designs of the liquid-propellant rocket engine and the rocket power unit.